This invention relates to a microswitch having the features recited in the prior art part of claim 1. The basic design of such switch has been described in two variants in "Luegers" Lexikon der Technik, Vol. 14 (1969) on pages 115, 116.
In the known switch a touch pin can be actuated so that a switching fork, which in its position of rest contacts a stationary contact, is moved toward an opposite stationary contact and is urged against the latter. Upon a decrease of the actuating force exerted on the touch pin, the switching fork jumps back to its initial position. In the second variant the switch is changed over by an overcenter spring when its dead center has been overcome. The switching mechanism for both embodiments of the microswitch is disposed in a housing, from which the terminals connected to the contacts protrude and into which the touch pin extends. During the soldering of the terminals, soldering fumes may enter the switch housing at least along the touch pin and may adversely affect the switching system.
A known switch, such as U.S. Pat. No. 4,565,592, comprises a base, which has a cylindrical aperture with an opening which is parallel to the axis of the cylinder. A substantially cylindrical cap has been inserted into the aperture and has a radial extension, which extends out of the aperture. The cap is open toward the base and receives the contact springs of the switch and can be rotated to deflect said contact springs. Particularly because the base and cap must be movable relative to each other there are gaps between the base and cap and soldering fumes and moisture may enter through said gaps.
The invention avoids the obvious attempt to seal in a conventional microswitch the passage in which the touch pin is guided. Instead, it is contemplated to use a switch housing which consists of a base and a cap, which is adapted to be closed by the base. Terminals provided on the base extend out through and are sealed to the base.
The switch can conveniently be handled in a position for use, which is provided in that the cap is pulled from the base out of the closed position. The switch can be actuated in a simple manner in position for use in that the cap is deflected to one side or the other and carries along the contact spring, which protrudes into the cap and is to be actuated, until the spring makes contact. For this reason the cap is not only a means which cooperates with the base to enclose the contact springs on all sides and to hermetically seal them but is also a means for actuating the switch in a very simple manner because the pivoted cap can directly act on the contact spring which is to be deflected without a need for any transmitting members which comprise levers and articulated joints such as are otherwise conventional in microswitches and co-determine and limit their life. In contrast, owing to its simple mechanical structure the switch in accordance with the invention affords considerable advantages as regards life and can be manufactured at lower cost. Besides, the cap does not need to be fixedly connected to the base; because the cap is inherently adjustable between a closed position, in which the cap is not pivotally movable, and a position for use, in which the cap is pivotally movable, the cap can be entirely pulled from the case so that it may be a loose part. This results in the advantage that different bases optionally provided with different sets of contact springs and different caps may be combined for different applications and for installation in different positions so that a family of switches can be provided by a modular system with a minimum expenditure.
In position for use the cap can be pivotally moved, on principle, in both directions and may then deflect one contact spring and the other so that the switch is more versatile in use than known microswitches. Alternatively the switch may optionally be designed to be actuated only in that the cap is pivotally moved in only one direction.
To ensure that the cap can easily be deflected defined manner for the function of the switch, the cap pivoted on two pins, which are mounted on the base.
To provide two clicked-in positions for the cap, it desirably carries at its open end two mutually opposite extensions. Said extensions are so designed that each of them is formed with an aperture for receiving the associated pin and in the aperture are formed with a waist, by which the aperture is divided and which can be overcome in that the extensions are elastically expanded so that the cap can snap on one side of the waist to its closed position and on the other side of the constriction to its position for use and cannot incidentally move from one position to the other.
The apertures in the extensions may consist of a slot having a waist or of an indentation having a waist. In that case it will be necessary to provide at the beginning of the indentation a constriction, which is similar to the waist restrains the cap in its clicked-in position.
The switch is particularly simple in its design and function and is nevertheless versatile. It permits different contact arrangements without a departure from its basic design. For instance, both contacts of a switch may be mounted on contact springs and said contact springs can be actuated as desired by a pivotal movement of the housing. On the other hand, the countercontact for a contact piece provided on a contact spring may consist of a stationary (fixed) contact, which may be indirectly secured to the base or directly to the inside surface of the cap and the lead connected to said fixed contact may extend out through the cap. The switch may be designed as a break switch and as a make switch.
There is also a simple possibility to provide the switch as a change-over switch by the provision of a further contact spring. In that case a third contact spring is provided between two contact springs and will be contacted by one contact spring or the other upon a pivotal movement of the cap.
To minimize the angular movement (actuating movement) to be performed by the cap, it will be desirable to provide in the cap a stop for the contact spring that is to be deflected. That stop is preferably so arranged that in the open switch the contact spring concerned contacts the stop only under a slight bias, if any. The stop is preferably adjustable, e.g., because it consists of an electrically insulating adjusting screw, which extends in a tapped bore of the cap and is accessible from the outside.
The contact springs usually carry elongate profiled contact pieces, which are provided in a crosswise arrangement and welded to the contact springs, and the base and the stops consist of an insulating material.